This project continues a series of experiments on the discrimination and identification of complex auditory patterns. The general purpose of this work is to determine the limits of human listeners' abilities to extract information from complex sounds, including especially those with temporal and spectral properties approximating speech. Experiments use criterion-controlled psychophysical methods in which listeners are trained until approaching asymptotic performance in various discrimination and identification tasks. Individual phoneme-length tonal components of word-length patterns can be resolved essentially as accurately as when those components are presented in isolation, but only when minimal-uncertainty testing procedures permit listeners to focus on a specific component. Under higher levels of stimulus uncertainty certain restricted spectral-temporal regions of the patterns (late, high-frequency components) are still resolved accurately, while most others are not. Measurements include: The spectral and temporal range of selective auditory attention, the time course of auditory perceptual learning, the manner in which gross properties of patterns can serve as cues to selectively attend to specific temporal components, informational limits on pattern discrimination, and listeners' abilities to learn to attend to multiple components within single patterns and to identify small "vocabularies" of patterns. The scope of this work is now being increased to include studies of individual differences in auditory pattern discrimination abilities among normal and impaired listeners, and in populations with certain language-related disabilities. Auditory patterns consisting of sequences of sounds synthesized to incorporate the source and resonant properties of the human vocal tract will also be investigated. The theoretical significance of the overall series of experiments is that it provides a link between auditory theories based on human listeners' abilities to detect and discriminate among isolated tones and theories of speech perception. This work has practical significance for impaired listeners, for whom sensitivity measures alone have been inadequate predictors of the help to be expected from hearing aids. Finally, use of a newly designed auditory discrimination test battery with learning and language-disordered listeners may help to resolve the issue of the possible auditory component in those disorders.